Stepped hollow wheel

ABSTRACT

A gear set for an internal gear machine. Both front areas of the first gearwheel include respectively one running area, which are axially spaced apart by a first gearwheel thickness, and the second gearwheel includes a thickness-reduced region which has a reduced gearwheel thickness in relation to the first gearwheel thickness.

FIELD

The present invention relates to the configuration and manufacture of a gear set of an internal gear machine, as well as an internal gear machine and a motor-pump unit.

BACKGROUND

It is known to use motor-pump units with internal gear machines in fully active damping systems of motor vehicles. Each shock absorber of the vehicle is hydraulically connected to a motor-pump unit associated therewith. The shock absorber thus becomes an active element, via which forces can be introduced into the chassis actively. This application of an internal gear machine in fully active damping system of motor vehicles involves special operating states, which usually do not occur outside of this special field of application. In the concrete case, the internal gear machine is frequently reversed while under pressure load, meaning that pressure is built up at a hydraulic connector, and while this pressure is still active, the rotation direction of the internal gear machine is already reversed.

Usually, leakage-compensated internal gear machines are employed, in which the axial leakage compensation takes place via so-called axial sealing disks, which are pressed frontally, in a manner depending on the working pressure, onto the gear set (comprising an externally toothed inner sprocket and an internally toothed hollow wheel), so that the gearwheels of the gear set slide in rotating manner on the planar axial sealing disks during operation. For this purpose both gearwheels of the gear set have planar running areas respectively on each of the front sides, said running areas usually extending over the entire front areas of the gearwheels. The axial sealing disks seal the two hydraulic working or pressure chambers (pressure and suction side) from one another and thus prevent a pump-internal leakage, which would have a negative impact on the volumetric efficiency of the internal gear machine. The forces acting on the axial disks are therefore adapted such that a resulting contact pressure force of the axial sealing disks onto the front sides of the gear set is always ensured.

Such a motor-pump unit with a leakage-compensated internal gear machine for reversing operation, which can thus work as an internal gear pump and/or as a hydraulic motor, is known, for example, from DE 10 2014 103 958 A1.

This axial leakage compensation allows for reducing the pump-internal leakage and therefore a very high volumetric efficiency, but generates friction, which has a negative impact on the hydraulic-mechanic efficiency.

The axial leakage compensation additionally generates reversing noises in the internal gear machine, which occur when the gear set ‘breaks free’ from standstill or upon slowly passing the zero point of rotation speed in the reversal point of the rotation direction, since it is necessary to build up a certain limit torque first in order to cause the gear set to rotate.

To reduce or suppress the reversal noises it is possible to first minimize the axial biasing force of the axial disks. However, said force can be reduced only conditionally, since the biasing force must ensure in any operating state that the axial sealing disks rest on the gear set frontally. If, in contrast, the axial disks were lifted during the operation of the pump, the already mentioned leakage would occur, since spaced-apart axial disks would create a pump-internal bypass between the two pressure or working chambers of the internal gear machine.

In applications such as the fully active damping systems, however, a good correlation between the rotation speed and the volume flow is important as well, for example when the rotation speed is measured on the electrical drive of the motor-pump unit and the volume flow of the unit is concluded therefrom.

SUMMARY

The object of the invention is to reduce the reversal noises, to achieve high volumetric efficiency, to suppress pump-internal leakage and/or to improve the hydraulic-mechanical efficiency.

The object is achieved by a gear set for an internal gear machine and a manufacturing method therefor, and by an internal gear machine and a motor-pump unit with the features of the independent claims. Preferred embodiments and developments are stated in the claims dependent thereon.

The gear set according to the invention for an internal gear machine is formed in a manner known per se by two gearwheels each having two axial front areas, meaning that the gear set comprises two gearwheels or consists thereof, namely an inner sprocket and a hollow wheel. Therein, at least the first gearwheel of the two gearwheels has (exactly) one running area on both opposing axial front areas. An axial distance of the two running areas measured in the direction of the rotation axis of the gearwheel is the first gearwheel thickness.

A running area of a gearwheel presently is an area section of a front area of the gearwheel, which is intended or suitable, during operation, i.e. during rotation of the gearwheel around its rotation axis, to slide on a corresponding non-rotating axial sealing element, which is usually planar in sections or fully planar, for example an axial sealing disk. For this purpose, the running area is an area section of the (axial) front area of the gearwheel that is fully or in every place planar or level. The axial height of the front area of the gearwheel is equal in every place of the running area and is predetermined, i.e. the axial height is continuously constant or remains the same. Correspondingly, the (surface of the) running area extends perpendicularly to the rotation axis and the surface normal of the front area of the gearwheel points in the direction of the rotation axis in every place of the running area.

In the simplest case, the running area extends over the entire respective front area of the respective gearwheel or generally only over a partial region of the front area.

It is generally conceivable here that the running area (for example the entirety of planar regions on the front area with predetermined or equal axial height on a given front area) consists of several area sections, which are separated by area sections with different, in particular smaller axial height (depressions, gaps, etc.), while one area section is continuously planar, and/or that the running area encloses area sections with different, in particular smaller axial height, which do not form part of the running area correspondingly.

However, the running area is preferably configured continuously and/or fully circumferentially around the rotation axis and/or consists of one single (continuously planar) area section. The running area correspondingly has at least one continuous or interruption-free path around the rotation axis on the respective front area. For example, the running area on the respective front area comprises or forms a planar, concentric and fully or continuously rotationally symmetric area section around the rotation axis, so that the running area extends continuously or in interruption-free manner between a minimal diameter and a larger maximal diameter on the front area and there are, in particular, no elevations and/or depressions (i.e. regions with greater or smaller axial height) present there. In the case of a fully or continuously rotationally symmetric running area, the front areas of the gearwheel teeth do not form part of the running area. The running area preferably also comprises the axial front areas of the gearwheel teeth, so that the running area forms, for example, an area section that is concentric and discretely rotationally symmetric around the rotation axis and has an n-fold discrete rotational symmetry (wherein n is the number of teeth of the gearwheel), which is correspondingly continuously planar or level between a minimal diameter and the maximal diameter. The minimal diameter is, for example, equal to zero or equal to the/an inner diameter of the gearwheel. The maximal diameter is equal to the/an outer diameter of the gearwheel, for example.

As already mentioned, in the simplest case the running area (with respect to its area) extends over 100% or over the entire front area of the first gearwheel, so that the running area is formed by the (entire) front area of the first gearwheel. Generally, the running area extends over a partial region or over exactly or at least a (continuous) area section of the front area of the respective gearwheel with a (total) area of 10% to 100% of the front area of the gearwheel, over for example 10%, 30%, 50%, 70%, 80%, 90%, 95%, 98% or 100% of the front area, wherein each of the stated values can also represent an upper or lower limit of the stated range of values.

The running area is created preferably by grinding (for example as the last manufacturing step which concerns this place of the front area), for example while rotating the gearwheel around its rotation axis, so that the running area is grinded or forms a grinded surface of the front area of the gearwheel.

If the first gearwheel, i.e. the gearwheel comprising the running area, is formed by the inner sprocket of the gear set, the maximal diameter of the running area is preferably a/the tooth-head circle diameter, i.e. the outer diameter of the inner sprocket, so that the running area of the inner sprocket particularly preferably extends over the entire front area of the inner sprocket outside of the minimal diameter of the running area and correspondingly comprises the axial front areas of the gearwheel teeth. The minimal diameter of the running area is preferably smaller than a/the tooth-base circle diameter of the inner sprocket and is particularly preferably equal to zero or equal to an inner diameter of the inner sprocket (such as at a shaft fitting).

If the first gearwheel, i.e. the gearwheel comprising the running area, is formed by the hollow wheel of the gear set, the minimal diameter of the running area is preferably a/the tooth-head diameter, i.e. the inner diameter of the hollow wheel, so that the running area of the hollow wheel extends particularly preferably over the entire front area of the hollow wheel within the maximal diameter of the running area and correspondingly comprises the axial front areas of the gearwheel teeth. The maximal diameter of the running area is preferably greater than a/the tooth-base circle diameter of the hollow wheel and is particularly preferably equal to an outer diameter of the hollow wheel.

According to the invention, the second gearwheel of the gear set further has at least or exactly one thickness-reduced region. In the thickness-reduced region(s) a gearwheel continuously (i.e. in every place of the thickness-reduced region) has a (n axial) gearwheel thickness that is reduced in relation to the first gearwheel thickness. A thickness-reduced region thus forms a tapered, stepped and/or recessed region. Generally, a gearwheel can comprise several, in particular differently defined thickness-reduced regions, for example with different axial height. Generally, a gearwheel thickness is the axial gearwheel thickness of the gearwheel, meaning the (axial) width or dimension of the gearwheel measured in the direction of the rotation or symmetry axis of the respective gearwheel (in the respective place of the front area of the gearwheel).

In relation to the prior art, where the complete front areas of both gearwheels of the gear set form the respective running areas, according to the invention, the total size of the friction area in the gear set is reduced by providing at least one thickness-reduced region. Correspondingly, friction during operation is reduced or the hydraulic-mechanical efficiency is increased and also the occurrence and/or the intensity of the reversal noise is reduced or prevented entirely.

Generally, a given thickness-reduced region can have different gearwheel thicknesses in different places on the front area of the gearwheel and different axial heights at its frontal or axial surfaces. However, the thickness-reduced region (or one of the thickness-reduced regions) is preferably a planar thickness-reduced region, in which both axial or frontal surfaces, which are respectively arranged on the two front areas of the gearwheel facing away from one another, form (entirely or continuously) planar or level area sections of the respective front area of the gearwheel and/or in which the respective axial heights of both frontal surfaces are respectively equal, identical and/or predetermined in every place. In this case, the entire surface or front area of the thickness-reduced region extends perpendicularly to the rotation axis, the surface normal of the front area of the gearwheel points in the direction of the rotation axis in every place of the thickness-reduced region and also the reduced thickness of the gearwheel is unchanging, constant and/or predetermined over the entire thickness-reduced region. Particularly preferably, the (both) frontal surfaces of a (planar) thickness-reduced region are also suitable or configured as running area.

A surface of the thickness-reduced region in the simplest case extends over the entire respective front area of the respective gearwheel or generally only over a partial region of the front area.

In particular in the case of a planar thickness-reduced region, it is generally possible that the (planar) surface consists of several area sections, which are separated by area sections with different, in particular smaller axial height (depressions, gaps, etc.), and/or that the (planar) surface of the thickness-reduced region encloses area sections with different, in particular smaller axial height. However, the surface of the thickness-reduced region is preferably configured continuously and/or entirely circumferentially around the rotation axis and/or consists of a single (continuous) area section. The (planar) surface of the thickness-reduced region correspondingly has at least one continuous or interruption-free path around the rotation axis on the respective front area. For example, the surface of the planar, thickness-reduced region comprises or forms a planar, concentric and fully or continuously rotationally symmetric area section around the rotation axis on the respective front area, so that the planar surface extends continuously or in interruption-free manner between a minimal diameter and a larger maximal diameter on the front area and that there are, in particular, no elevations and/or depressions (i.e. regions with greater or smaller axial height) present there. In the case of a fully or continuously rotationally symmetric surface, the front areas of the gearwheel teeth do not form part of the surface of the thickness-reduced region. Alternatively, the surface of the thickness-reduced region also comprises the axial front areas of the gearwheel teeth, so that the surface of the thickness-reduced region forms, for example, an areal section that is concentric and discretely rotationally symmetric around the rotation axis and has an n-fold discrete rotational symmetry (wherein n is the number of teeth of the gearwheel), which is correspondingly continuously planar or level between a minimal diameter and the maximal diameter. The minimal diameter is equal to zero or equal to the/an inner diameter of the gearwheel, for example. The maximal diameter is equal to the/an outer diameter of the gearwheel, for example.

As already mentioned, the thickness-reduced region can extend over the entire gearwheel, so that on a given front area of the gearwheel there extends the surface of the thickness-reduced region (with respect to areal extension) over 100% of the gearwheel and thus the entire front area of the respective gearwheel forms the surface of the thickness-reduced region. Generally, the surface of the at least or exactly one thickness-reduced region extends over a partial region of the front area of the respective gearwheel with a (total) area of 10% up to 100% of the front area of the gearwheel, over for example 10%, 30%, 50%, 70%, 80%, 90%, 95%, 98% or 100% of the front area, wherein each of the stated values can also represent an upper or lower limit of the stated range of values.

In the case of a planar thickness-reduced region, the planar surfaces thereof are preferably created by grinding (for example as the last manufacturing step which concerns this place of the front area), for example while rotating the gearwheel around its rotation axis, so that the planar surface of the thickness-reduced region is grinded or forms a grinded area section of the front area of the gearwheel.

If the second gearwheel or the gearwheel comprising the thickness-reduced region is formed by the hollow wheel of the gear set, the maximal diameter of the thickness-reduced region is preferably a/the outer diameter of the hollow wheel, so that the surface of the thickness-reduced region particularly preferably extends over the entire front area of the hollow wheel outside of the minimal diameter of the thickness-reduced region. The minimal diameter of the running area is preferably greater than a/the tooth-base circle diameter of the hollow wheel or equal to an inner diameter of the hollow wheel.

If the second gearwheel or the gearwheel comprising the thickness-reduced region is formed by the inner sprocket of the gear set, the minimal diameter of the thickness-reduced region is preferably equal to zero or a/the inner diameter of the inner sprocket (such as at a shaft fitting), so that the surface of the thickness-reduced region particularly preferably extends over the entire front area of the inner sprocket within the maximal diameter of the thickness-reduced region. The maximal diameter of the thickness-reduced region is preferably smaller than a/the tooth-base circle diameter of the inner sprocket and/or equal to an outer diameter of the inner sprocket.

Preferably, a running area has the greatest axial height on the respective front area of the respective gearwheel. In other words, preferably a running area forms the surface of the respective front area of the gearwheel that is disposed the furthest outside axially or that is disposed at the greatest distance from an axial center plane of the respective gearwheel. If the running areas on both front areas of a gearwheel that are axially spaced apart by the first gearwheel thickness have the greatest axial height, the first gearwheel thickness constitutes the maximal thickness of the gearwheel at the same time. Particularly preferably, the first gearwheel thickness also constitutes the maximal (axial) thickness or gearwheel thickness of the entire gear set.

In a preferred embodiment of the gear set according to the invention, on the second gearwheel the two axial surfaces of the thickness-reduced region have the greatest axial height of the entire respective front area of the respective gearwheel. In other words, the surface of the thickness-reduced region preferably forms the surface of the respective front area of the gearwheel that is disposed the furthest outside axially or that is disposed at the greatest distance from the axial center plane of the gearwheel. Correspondingly, the second gearwheel has a gearwheel thickness in every place that is reduced in relation to the first gearwheel thickness, so that the second gearwheel consists entirely of one or several thickness-reduced regions. The maximal thickness of the second gearwheel in this case is smaller than the first gearwheel thickness. Preferably, the second gearwheel consists of exactly one preferably planar, thickness-reduced region, i.e. the thickness-reduced region extends over the entire second gearwheel. Correspondingly, both front areas of the second gearwheel consist respectively (entirely) of the frontal surface(s) of the thickness-reduced region(s). Preferably, the thickness reduction, i.e. the difference between the reduced gearwheel thickness of the thickness-reduced region and the first gearwheel thickness of the running areas of the first gearwheel, is in the range between 4 μm and 10 μm or between 3 μm and 30 μm or between 2 μm and 50 μm and/or amounts to, for example, 2, 3, 4, 5, 6, 8, 10, 15, 20, 30, 40 or 50 μm, wherein each of the stated values can also represent an upper or lower limit of the range of values. In this preferred embodiment the second gearwheel has no running areas which are axially spaced apart by the first gearwheel thickness.

In an alternative, preferred embodiment of the gear set or of the second gearwheel according to the invention, both front areas of the second gearwheel comprise the respective frontal surface of the at least or exactly one thickness-reduced region and additionally one running area, or consist thereof, wherein the running areas of the two front areas are axially spaced apart by the first gearwheel thickness. The running areas of the second gearwheel thus, besides the running areas of the first gearwheel, form further running areas in the gear set and can have the configuration features already described above. Preferably, the running areas on the second gearwheel also have the greatest axial height of the respective front area.

The presence of running areas on the second gearwheel, said running areas being axially spaced apart by the first gearwheel thickness, allows for choosing a greater thickness reduction, i.e. thickness difference between the reduced gearwheel thickness of the thickness-reduced region of the second gearwheel and the first gearwheel thickness of the running areas. The thickness reduction of the thickness-reduced region of the second gearwheel preferably amounts to at least 2, 4, 6, 10, 20, 50, 100, 200 or 500 μm or is in a range between 4 μm and 10 μm or between 3 μm and 30 μm or between 2 μm and 50 μm and/or amounts to, for example, 2, 3, 4, 5, 6, 8, 10, 15, 20, 30, 40 or 50 μm, wherein each of the stated values can also represent an upper or lower limit of the range of values. Preferably, on each front area of the second gearwheel, the respective surface of the thickness-reduced region and the respective running area directly adjoin one another, particularly preferably along a concentric and/or closed circular path around the rotation axis of the second gearwheel. Generally, the thickness reduction of the thickness-reduced region can be implemented by an axial height difference between the running area and the surface of the thickness-reduced region on only one of the two front areas of the second gearwheel, while, for example, on the opposite front area the running area and the surface of the thickness-reduced region form a continuously planar area section of the front area. However, the surfaces of the thickness-reduced regions on both front areas preferably have a smaller axial height than the respective running areas, so that preferably on both front areas in radial direction a concentric and/or stepped transition is present between these area sections on the front area. Further preferably, on both front areas of the second gearwheel the axial height difference between respectively the surface of the thickness-reduced region and the (adjoining) running area is equal and/or amounts to one half of the thickness reduction. The second gearwheel is particularly preferably configured to be mirror-symmetric with reference to its axial central plane.

In a preferred embodiment of the gear set according to the invention, the running areas on both front areas of the first gearwheel respectively have the greatest axial height of the front area in question, as already described in detail further above.

In the simplest case, the running areas of the first gearwheel form the entire front areas, as likewise described in detail above. In an alternative embodiment of the gear set or the first gearwheel, the first gearwheel also comprises a thickness-reduced region, so that both front areas of the first gearwheel comprise or consist of the respective running area and a frontal surface of the thickness-reduced region. The thickness-reduced region of the first gearwheel thus forms at least one further thickness-reduced region in the gear set in addition to the thickness-reduced region(s) of the second gearwheel. The thickness-reduced region and its frontal surfaces can have the configuration features already described above.

The presence of running areas on the first gearwheel in turn allows for choosing a greater thickness reduction, as already described above, on the first gearwheel. The thickness reduction of the thickness-reduced region of the first gearwheel preferably amounts to at least 2, 4, 6, 10, 20, 50, 100, 200 or 500 μm or is in a range between 4 μm and 10 μm or between 3 μm and 30 μm or between 2 μm and 50 μm and/or amounts to, for example, 2, 3, 4, 5, 6, 8, 10, 15, 20, 30, 40 or 50 μm, wherein each of the stated values can also represent an upper or lower limit of the range of values.

Preferably, on each front area of the first gearwheel, the respective surface of the thickness-reduced region and the respective running area immediately adjoin one another, particularly preferably along a concentric and/or closed circular path around the rotation axis of the first gearwheel. Generally, the thickness reduction of the thickness-reduced region can be implemented by an axial height difference between the running area and the surface of the thickness-reduced region on only one of the two front areas of the first gearwheel, while, for example, on the opposite front area the running area and the surface of the thickness-reduced region form a continuously planar area section of the front area. However, the surfaces of the thickness-reduced regions on both front areas preferably have a smaller axial height than the respective running areas, so that preferably on both front areas in radial direction a concentric and/or stepped transition is present between these area sections on the front area. Further preferably, on both front areas of the first gearwheel the axial height difference between respectively the surface of the thickness-reduced region and the (adjoining) running area is equal and/or amounts to one half of the thickness reduction. The first gearwheel is particularly preferably configured to be minor-symmetric with reference to its axial central plane.

In the manufacturing method according to the invention, in a first step initially a gear set with two gearwheels is supplied, namely an inner sprocket and a hollow wheel. Each axial front area of the two gearwheels respectively comprises (at least) one running area. The running areas arranged on opposite front areas are axially spaced apart by the first gearwheel thickness. The running areas of the front areas in the supplied gear set extend respectively in at least a partial region of the respective front area, in particular at least in the running areas to be created and preferably also in the surfaces of the thickness-reduced regions to be created. Preferably, the running areas on both front areas of both gearwheels extend respectively over the entire front area.

This supplying of the gearwheels of the gear set preferably takes place by jointly frontally grinding both gearwheels, i.e. both gearwheels of the gear set are grinded at the same time and/or grinded in the same grinding apparatus and/or exposed to the identical grinding process, for example. This allows for a cost-effective and highly precise manufacture of the gearwheels to be supplied, in particular in such a manner that all running areas of a given gearwheel are axially spaced apart by the first gearwheel thickness.

The gearwheels are preferably grinded over the entire respective front area and preferably the entire front areas are grinded continuously or over the full area (namely when no gaps and/or depressions or thickness-reduced regions are present on the front areas). Correspondingly, the running areas of the supplied gearwheels or of the supplied gear set are grinded areas and/or the axially furthest outwardly disposed surfaces of the respective front area of the supplied gearwheels or of the supplied gear set.

According to the invention, subsequently the thickness-reduced region at least of the second gearwheel to be created is created by (possibly further or additional) grinding of the second gearwheel, which takes place over the entire front area or only in certain regions, namely on the thickness-reduced region to be created, on exactly one or on both front areas of the second gearwheel. In the latter case, material is grinded off on both front areas of the second gearwheel, so that, in relation to the supplied and/or—in the case of grinding only in certain regions—in relation to the remaining, residual front or running area of the second gearwheel, a surface with reduced axial height is created on both front areas. This frontal thickness reduction is preferably equal on both front areas of the second gearwheel and amounts to one half of the thickness reduction (thickness difference between the reduced gearwheel thickness and the first gearwheel thickness). Alternatively, the thickness-reduced region can be created by (only) one-sided grinding, so that the reduced axial height is equal to the thickness reduction. This further grinding of the second gearwheel preferably takes place in a method step immediately following the joint grinding and/or in the same grinding apparatus and/or the identical grinding process as the joint grinding.

In a preferred embodiment of the manufacturing method according to the invention—to create a thickness-reduced region also on the first gearwheel—the first gearwheel is additionally exposed to a further or additional grinding in certain regions. Also here, preferably material is grinded off on both front areas, so that in relation to the remaining front area, which forms the respective running area in the simplest case, a surface with reduced axial height is created. This frontal thickness reduction is preferably equal on both front areas of the first gearwheel and amounts to one half of the thickness reduction (thickness difference between the reduced gearwheel thickness and the first gearwheel thickness). This further grinding of the first gearwheel preferably takes place in a method step immediately following the joint grinding or the grinding of the second gearwheel and/or in the same grinding apparatus and/or the identical grinding process. This further grinding of the first gearwheel in certain regions can generally have the same configuration features as the grinding of the second gearwheel in certain regions described above, and can be provided only on one side in particular.

Particularly preferably, the grinding in certain regions of the first and/or the second gearwheel takes place exclusively outside of the front areas of the gearwheel teeth, so that the thickness-reduced region on the first and/or the second gearwheel is particularly preferably configured to be fully or continuously rotationally symmetric.

In a preferred embodiment of the gear set according to the invention both running areas of the first gearwheel respectively have the greatest axial height of the respective front area. In the simplest case, each running area extends over the entire front area of the first gearwheel. Further, the thickness-reduced region of the second gearwheel is a planar, thickness-reduced region, the frontal surfaces of which respectively have the greatest axial height on the respective front areas. In the simplest case, the thickness-reduced region extends over the entire second gearwheel, so that the surfaces of the thickness-reduced region extend over the entire respective front area of the second gearwheel. A thus configured gear set requires no grinding in certain regions and/or can be manufactured exclusively by grinding over the entire front area of the gearwheels, which simplifies the manufacturing process and renders it more cost-effective.

In this embodiment, the thickness reduction, i.e. the thickness difference between the reduced gearwheel thickness of the thickness-reduced region of the second gearwheel and the first gearwheel thickness of the first gearwheel, is in a range between 4 μm and 10 μm or between 3 μm and 30 μm or between 2 μm and 50 μm and/or amounts to, for example, 2, 3, 4, 5, 7, 10, 20, 30, 40 or 50 μm, wherein each of the stated values can also represent an upper or lower limit of the range of values.

On one or every gearwheel of the gear set preferably the two running areas arranged on the opposite front areas of the gearwheel, are arranged in the axial direction on the respective gearwheel, preferably in overlapping manner and/or particularly preferably congruently or mirror-symmetrically (with reference to a central or symmetry plane of the gearwheel, which stands perpendicularly on the rotation axis of the gearwheel), so that the two running areas are configured on the two front areas in mutually corresponding manner, i.e. in a mirror-image manner and/or identically, with respect to shape, position, size, surface area, etc. Correspondingly, the gearwheel has an unvarying, constant and/or predetermined gearwheel thickness which is equal to the first gearwheel thickness, exactly or at least in the overlap region of the two running areas or (when the running areas are arranged congruently) on the entire running area of a front area.

Further, the first and/or the second gearwheel is preferably configured to be entirely mirror-symmetric with reference to the central or symmetry plane of the first gearwheel and/or has (possibly with the exception of a possible shaft fitting) an n-fold discrete rotational symmetry with reference to the rotation axis (with n equaling the number of teeth of the respective gearwheel).

The first gearwheel is preferably the inner sprocket and the second gearwheel is the hollow wheel of the gear set or the first gearwheel is the hollow wheel and the second gearwheel is the inner sprocket of the gear set.

The first and/or the second gearwheel is preferably configured in one piece, i.e. made of one piece and/or is a work piece constructed from a homogeneous material. The first and the second gearwheel consist of different materials or of the same material. Alternatively, the first and/or the second gearwheel is configured in single-piece manner, i.e. it is put together from a multiplicity of (one-piece) components of different materials or of respectively the same material, usually in inseparable or irreversible manner, in particular prior to a frontal grinding during manufacture. The surfaces or the front sides of the first and/or the second gearwheel are preferably hardened, tempered and/or sintered. The material employed (or each of the materials employed) is as a rule a metal or metal alloy, in particular steel, brass, cast iron, aluminum and/or copper.

The (outer) diameter of the inner sprocket is preferably in the range between 5 and 100 mm and amounts to, for example, 5, 10, 20, 30, 50, 70 or 100 mm, wherein each of the stated values can also represent an upper or lower limit of the range of values.

The number of teeth of the inner sprocket is preferably in a range between 10 and and amounts to, for example, 10, 12, 15, 20, 25, 30 or 40 teeth, wherein each of the stated values can also represent an upper or lower limit of the range of values.

The (outer) diameter of the hollow wheel is preferably in the range between 20 and 150 mm and amounts to, for example, 20, 30, 40, 50, 70, 100, 120 or 150 mm, wherein each of the stated values can also represent an upper or lower limit of the range of values.

The inner diameter or tooth-head circle diameter of the hollow wheel is in the range between 10 and 140 mm and amounts to, for example, 10, 20, 30, 50, 60, 90, 110 or 140 mm, wherein each of the stated values can also represent an upper or lower limit of the range of values.

The number of teeth of the hollow wheel is preferably in the range between 12 and and amounts to, for example, 12, 15, 20, 25, 30, 40 or 50 teeth, wherein each of the stated values can also represent an upper or lower limit of the range of values.

The ratio of the number of teeth of the inner sprocket to that of the hollow wheel is in the range between 2:3 and 4:5 and amounts to, for example, 2:3, 2.5:3.5, 3:4, 3.5:4.5 or 4:5, wherein each of the stated values can also represent an upper or lower limit of the range of values.

The first gearwheel thickness is preferably in the range between 5 and 50 mm and amounts to, for example, 5, 8, 10, 13, 15, 20, 25, 30, 40 or 50 mm, wherein each of the stated values can also represent an upper or lower limit of the range of values.

The invention further relates to an internal gear machine (internal gear pump, hydraulic motor, etc.) with a gear set as described above. In a manner known per se, the internal gear machine further comprises axial sealing elements, preferably in the form of one or two axial sealing disks or axial housing parts or housing sections, which serve for compensating or suppressing axial leakage. These are preferably axially movable and/or axial sealing disks with intrinsic pressure applied thereto, such as described in DE 10 2014 103 958 A1, for example. The content of this document, in particular the section “internal gear machine” and “axial compensation” is hereby included in the disclosure content of the present document. The axial sealing disks have a surface corresponding to the gear set, preferably a planar sliding or running area, which can have depressions or interruptions, but has at least no elevations in the running region of the gearwheels of the gear set and is adapted for frontal, rotational sliding of the gearwheels.

The internal gear machine preferably further comprises a housing with hydraulic connectors, in particular two hydraulic connectors for flow and return to/from a load, in particular a shock absorber. Further, the internal gear machine preferably comprises a working fluid, in particular a hydraulic fluid, preferably a gear oil and/or Pentosin CHF 11S (from FUCHS PETROLUB SE, formerly Deutsche Pentosin-Werke GmbH) and/or with a (kinematic) viscosity between 500 and 3×10⁻⁶ m²/s in the temperature range between −30° C. and 150° C., in particular 17 to 20×10⁻⁶ m²/s at 40° C. The internal gear machine is preferably adapted for a working pressure of (up to) 10, 20, 30, 50, 80, 100, 150, 200 or 250 bar.

The invention further relates to a motor-pump unit with an internal gear machine as described above. In a manner known per se, the motor-pump unit further comprises a mechanical drive shaft which connects the inner sprocket to a motor, preferably an electric motor or electric motor generator and transmits torques between the motor and the inner sprocket or the internal gear machine during operation. Preferably, the motor-pump unit is adapted to work in alternating or reversing operation, i.e. alternatingly as an internal gear pump mechanically driven by the electric motor and/or as a hydraulic motor mechanically driving the electric motor generator. The motor-pump unit further comprises preferably a suitable electronic control unit ECU for the motor, which is adapted, in particular, for maximal reversing or reversal frequencies up to 10 Hz, up to 20 Hz, up to 30 Hz or up to Hz. The motor-pump unit is preferably a construction unit in which the electronic control unit, the motor and the internal gear machine are firmly connected to one another and/or arranged in a common housing, which is preferably airtight, waterproof and/or splash-waterproof.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will hereinafter be described by way of example with reference to the attached drawings. The drawings are merely schematic representations and the invention is not limited to the specific represented embodiment examples.

FIG. 1A is a view of a gear set, an internal gear machine and a motor-pump unit, and

FIG. 1B is a view of a gear set, an internal gear machine and a motor-pump unit, and

FIG. 1C is a view of a gear set, an internal gear machine and a motor-pump unit, and

FIG. 2A shows a perspective sectional view of a gear set supplied in the manufacturing method, and

FIG. 2B shows a sectional view of embodiment examples of gear sets with thickness-reduced regions.

FIG. 2C shows a sectional view of embodiment examples of gear sets with thickness-reduced regions.

FIG. 2D shows a sectional view of embodiment examples of gear sets with thickness-reduced regions.

DETAILED DESCRIPTION

In the FIGS. 1A to 1C the components of a gear set, an internal gear machine 10 and of a motor-pump unit are represented, which are respectively substantial for the invention. Details going beyond this can be gathered, for example, from the document DE 10 2014 103 958 A1 already stated above.

The gear set firstly comprises an externally toothed inner sprocket 11 and an internally toothed hollow wheel 12, which mutually engage eccentrically and, depending on the rotation direction, pump a working fluid or hydraulic fluid between two working or pressure chambers which are, among other things, separated by a radial sealing element 13. The radial sealing element 13, also referred to as sickle element, serves for radially compensating or sealing against leakage between the two adjoining pressure chambers.

So-called axial sealing disks 14, as schematically represented in the perspective exploded view of FIG. 1B, serve for sealing against axial leakage. These create planar areas on which the inner sprocket 11 and the hollow wheel 12 slide in rotating manner during operation. The axial sealing disks 14 can also contain depressions or gaps, which are not represented, and are, for example, subjected to the working pressure of the internal gear machine 10, so that the two axial sealing disks 14 clamp the inner sprocket 11 and the hollow wheel 12 in sealing manner.

The inner sprocket 11 of the internal gear machine 10 is connected via a shaft 21 to an electric motor 20, which can also be configured as an electric motor generator. Correspondingly, the electric motor generator 20 can drive the internal gear machine 10 or, vice versa, the internal gear machine 10 drives the electric motor generator 20 (for example during recuperation operation).

The internal gear machine 10, the electric motor generator 20 and an electronic control unit 30 are firmly interconnected and form a common construction unit in the embodiment example shown (see FIG. 1C). The respective housing parts of the internal gear machine 10, the electric motor generator 20 and the electronic control unit 30 form a common housing, so that a compact construction type results. Further, the internal gear machine 10 has hydraulic connectors 15, which connect the pressure chambers of the internal gear machine 10 with a load, for example a shock absorber.

In the FIGS. 2A-2D various gear sets are represented in cross section along the line AA′ drawn in FIG. 1A. While FIG. 2A shows a perspective sectional view along the entire line AA′, in the FIGS. 2B to 2D the respective gear sets are represented only along the left part (in FIG. 2A) of the line AA′ as a simple sectional view.

FIG. 2A shows an embodiment example of a gear set, as supplied in the first step of the manufacturing method according to the invention or as present prior to the grinding of the thickness-reduced region according to the invention. For this purpose the inner sprocket 11 and the hollow wheel 12 were subjected to a joint grinding process so that both front sides of both gear wheels 11, 12 of the gear set are grinded to be completely planar and have the first gear wheel thickness in every place. The front areas of the inner sprocket 11 and the hollow wheel 12 thus form running areas at the same time and are already suitable in this form for employment as a gear set of an internal gear machine 10, as is already known from the state of the art in particular.

In the sectional views of the FIGS. 2A-2D the sprocket or tooth areas are hatched. FIG. 2A represents, for the inner sprocket 11, the tooth-base circle diameter 16 and the tooth-head circle diameter 17, which represents the (outer) diameter of the inner sprocket 11 at the same time. Likewise, the hollow wheel 12 also has a tooth-base circle diameter and a tooth-head circle diameter, wherein the latter forms the inner diameter of the hollow wheel 12 at the same time.

According to the invention, proceeding from the gear set represented in FIG. 2A, on at least one of the two gearwheels a thickness-reduced region is created which has a reduced gearwheel thickness.

In the simplest case, exactly one of the two gearwheels is subjected to a further or additional grinding process over its entire front area(s), i.e. in the simplest case over the full area, so that the thickness-reduced region thus created extends over the entire gearwheel. In the embodiment example represented in FIG. 2B the hollow wheel 12 (in this embodiment example corresponding to the second gearwheel) is subjected to the additional grinding process over its entire area, so that the resulting thickness-reduced region extends over the entire hollow wheel 12, while the inner sprocket 11 (in this embodiment example corresponding to the first gearwheel) continues having the first gearwheel thickness in every place of its front area. In the embodiment example represented in FIG. 2C the inner sprocket 11 (in this embodiment example corresponding to the second gearwheel) is subjected to the additional grinding process over its entire area, so that the resulting thickness-reduced region extends over the entire inner sprocket 11, while the hollow wheel 12 (in this embodiment example corresponding to the first gearwheel) continues having the first gearwheel thickness in every place of its front area.

In the embodiment example represented in FIGS. 2B and 2C the hollow wheel 12 has an outer diameter of 52 mm and 20 sprocket teeth. The inner sprocket 11 has an outer diameter of 30 mm and 15 sprocket teeth. Further, the first gearwheel thickness amounts to 13 mm and the thickness reduction, i.e. the thickness difference between the thickness-reduced region and the first gearwheel thickness amounts to 6 μm. These dimensions—where applicable—are also valid for the other embodiment examples.

It is generally also possible to provide the thickness-reduced region on one or on both gearwheel(s) only in certain regions, as represented for both gearwheels by way of example in the embodiment example of FIG. 2D. A concentric thickness-reduced region is created in an inner region of the inner sprocket 11, said region not extending over the sprocket teeth in the represented embodiment example. The maximal diameter of the thickness-reduced region of the inner sprocket 11 is presently the tooth-base circle diameter, and the minimal diameter is the inner diameter or the shaft fitting of the inner sprocket 11. At the same time or alternatively, a concentric thickness-reduced region is created in an outer region of the hollow wheel 12, which likewise does not extend over the sprocket teeth in the represented embodiment example. The maximal diameter of the thickness-reduced region of the hollow wheel 12 is presently the outer diameter, and the minimal diameter is the tooth-base circle diameter of the hollow wheel 12.

In the not thickness-reduced regions, which are not subjected to further grinding, the previous surface is maintained, usually the running areas on the respective front area, which extends over the front areas of the sprocket teeth in the represented embodiment example, and thereby continues ensuring efficient axial leakage sealing. In the case of a reduced gearwheel thickness provided only in certain regions of a front area, a stronger thickness reduction can be provided, presently a thickness reduction of 200 μm.

In further, not represented embodiment examples, the various configuration possibilities of the gearwheels are combined:

-   -   inner sprocket 11 with reduced gearwheel thickness in certain         regions and hollow wheel 12 without thickness-reduced region,     -   inner sprocket 11 with reduced gearwheel thickness in certain         regions and hollow wheel 12 with thickness-reduced region         extending over the entire hollow wheel 12,     -   hollow wheel 12 with reduced gearwheel thickness in certain         regions and inner sprocket 11 without thickness-reduced region,         and     -   hollow wheel 12 with reduced gearwheel thickness in certain         regions and inner sprocket 11 with thickness-reduced region         extending over the entire inner sprocket 11.

In the embodiment example represented in FIG. 2D or generally in the case of reduced gearwheel thickness only in certain regions, the supplying of the thickness-reduced region on the inner sprocket 11 and/or the hollow wheel 12 takes place through additional grinding on both sides, so that the axial height difference between the thickness-reduced regions and the (supplied) running areas is identical on both front areas. Correspondingly, the gearwheels are mirror-symmetric with reference to an axial central plane of the respective gearwheel.

In a not represented embodiment example the grinding process is carried out asymmetrically, so that on both front areas of a given gearwheel there result mutually differing axial height differences between the (supplied) running area and the surface of the thickness-reduced region.

In a further not represented embodiment example, the additional grinding process is effected only on one side, so that there result axial height differences between the surface of the thickness-reduced region and the (supplied) running area only on one front area, whereas on the opposite front area the surface of the thickness-reduced region and the running area form a continuously planar surface or running area.

LIST OF REFERENCE NUMERALS

-   -   10 internal gear machine     -   11 inner sprocket     -   12 hollow wheel     -   13 radial sealing element     -   14 axial sealing disk     -   15 hydraulic connectors     -   16 tooth-base circle diameter     -   17 tooth-head circle diameter     -   20 electric motor, electric motor generator     -   21 shaft, drive shaft     -   30 ECU—electric control unit 

1. A gear set for an internal gear machine, formed of two gearwheels each having two axial front areas, wherein both front areas of the first gearwheel comprise respectively one running area, which are axially spaced apart by a first gearwheel thickness, and wherein the second gearwheel comprises a thickness-reduced region which has a gearwheel thickness that is reduced in relation to the first gearwheel thickness.
 2. The gear set according to claim 1, wherein the thickness-reduced region of the second gearwheel is a planar region, and/or both surfaces of the thickness-reduced region of the second gearwheel respectively have the greatest axial height of the respective front area, and/or the thickness-reduced region extends over the entire second gearwheel, and/or a thickness reduction of the thickness-reduced region is in a range between 2 μm and 50 μm or between 3 μm and 30 μm or between 4 μm and 10 μm.
 3. The gear set according to claim 1, wherein both front areas of the second gearwheel comprise a surface of the thickness-reduced region and a running area or consist thereof, wherein the running areas of the two front areas of the second gearwheel are axially spaced apart by the first gearwheel thickness, and wherein the running areas respectively have the greatest axial height of the respective front area, and/or the thickness-reduced region of the second gearwheel is a planar region, and/or a thickness reduction of the thickness-reduced region amounts to at least 2, 4, 6, 10, 50, 100, 200 or 500 μm or is in a range between 2 μm and 50 μm or between 3 μm and 30 μm or between 4 μm and 10 μm, and/or an axial height difference between the surface of the thickness-reduced region and the running area is identical on both front areas and/or amounts to one half of the thickness reduction.
 4. The gear set according to claim 1, wherein on one or both front area(s) of the first gearwheel the running area respectively has the greatest axial height of the respective front area, and/or one or both front area(s) of the first gearwheel consist of the respective running area, or the first gearwheel comprises a thickness-reduced region, so that the front areas of the first gearwheel comprise the respective running area and a surface of the thickness-reduced region or consist thereof, wherein preferably the thickness-reduced region of the first gearwheel is a planar region, and/or a thickness reduction of the thickness-reduced region amounts to at least 2, 4, 6, 10, 50, 100, 200 or 500 μm or is in a range between 2 μm and 50 μm or between 3 μm and 30 μm or between 4 μm and 10 μm, and/or an axial height difference between the surface of the thickness-reduced region and the running area on both front areas is identical and/or amounts to one half of the thickness reduction.
 5. The gear set according to claim 1, wherein both running areas of the first gearwheel respectively have the greatest axial height of the respective front area and preferably both running areas respectively form the front areas of the first gearwheel, and the thickness-reduced region of the second gearwheel is a planar, thickness-reduced region, the frontal surfaces of which respectively have the greatest axial height and/or respectively form the front areas of the second gearwheel, and wherein preferably a thickness reduction is in a range between 2 μm and 50 μm or between 3 μm and 30 μm or between 4 μm and 10 μm.
 6. The gear set according to claim 1, wherein the running areas on one gearwheel or respectively on both gearwheels are arranged in the axial direction in overlapping manner and/or congruently or mirror-symmetrically and/or the first gearwheel thickness is present continuously in the overlap region and/or on the entire running area(s), and/or the first gearwheel thickness is the maximal thickness of the respective gearwheel or of the gear set, and/or one or each running area is continuously rotationally symmetric or discretely rotationally symmetric and/or one or each running area comprises the front areas of the gearwheel teeth.
 7. The gear set according to claim 1, wherein the first and/or the second gearwheel is configured to be mirror-symmetric and/or has an n-fold discrete rotational symmetry with reference to the rotation axis, wherein n is the number of teeth of the gearwheel.
 8. The gear set according to claim 1, wherein at least one or all running areas and/or planar surfaces of thickness-reduced regions are grinded surfaces and/or have constant axial heights.
 9. The gear set according to claim 1, wherein the first gearwheel is the inner sprocket and the second gearwheel is the hollow wheel or the first gearwheel is the hollow wheel and the second gearwheel is the inner sprocket.
 10. The gear set according to claim 1, wherein the first and/or second gearwheel is configured in one-piece or single-piece manner and/or the first and second gearwheel consist of different materials or of the same material.
 11. The gear set according to claim 1, wherein the inner sprocket has a diameter between 5 and 100 mm, in particular of 30 mm, and has 10 to 30 teeth, in particular 15 teeth, and/or the hollow wheel has an outer diameter between 20 and 150 mm, in particular of 52 mm, an inner diameter between 10 and 140 mm, in particular 40 mm, and has 12 to in particular 20 teeth, and/or the ratio of the number of teeth of the inner sprocket to the hollow wheel amounts to between 2:3 and 4:5 and in particular is 3:4, and/or the first gearwheel thickness is between 5 and 50 mm and in particular amounts to 13 mm.
 12. An internal gear machine, comprising: a gear set according to claim 1, and axial sealing elements, in particular one or two axial sealing disks or axial housing parts, and preferably further comprising a housing with hydraulic connectors, and/or a hydraulic fluid, in particular a gear oil and/or Pentosin CHF 11S and/or with a viscosity between 500 and 3×10⁻⁶ m²/s in a temperature range between −30° C. and 150° C.
 13. A motor-pump unit, comprising: an internal gear machine according to claim 12, and a shaft which connects the inner sprocket to a motor, wherein the motor-pump unit is preferably adapted for reversing operation and/or the motor is an electric motor generator.
 14. A method for manufacturing a gear set according to claim 1, comprising the steps of: supplying the first and the second gearwheel, the axial front areas of which comprise respectively one running area or consist thereof, wherein the running areas are axially spaced apart by the first gearwheel thickness and wherein preferably the supplying takes place through joint frontal grinding of both gearwheels, and grinding in certain regions or over the full area of the second gearwheel for configuring the thickness-reduced region of the second gearwheel.
 15. The method according to claim 14, comprising the further step of grinding in certain regions of the first gearwheel for configuring the thickness-reduced region of the first gearwheel. 